Movement-control switches



May 6 F. c. BOYCE ETAL 3,183,319

MOVEMENT-CONTROL.SWITQHES- A Filed Nov. 27 1962" v I 2 Sheets-Sheet 1 y 1965 F. c. BOYCE ETAL 3,183,319

MOVEMENT-CONTROL SWITCHES I I Filed Nov. 27, 1962 2 Sheets-Sheet 2 United States Patent 3,183,319 MOVEMENT-CONTROL SWITCHES Frederick Charles Boyce, Swindon, and Peter John Fogaty,

Ashburton, England, assignors, by mesne assignments, to The Birmingham Small Arms Company Limited, Birmingham, England Filed Nov. 27, 1962, Ser. No. 240,477 Claims priority, application Great Britain, July 26, 1962, 28,823/ 62 8 Claims. (Cl. 200-47) This invention relates to movement-control switches, that is to say to switches which serve to terminate or reverse movement of a machine-tool slide or other motordriven element and has for an object to provide an improved switch construction permitting a substantial amount of over-travel of the switch-controlling member at the end of the switch-actuating stroke. According to the invention a switch-actuating rocker lever is itself actuated by a pair of abutments rotatable with a switch-actuating shaft and co operating with abutment surfaces on the rocker lever, arranged symmetrically to each other at opposite sides of a plane containing the rocking axis of the said lever, said surfaces extending at an angle to the radial plane through the said axis, each abutment surface being so limited as to move out of engagement with the co-operating abutment when the rocker lever has reached one of its terminal positions, co-operating pairs of stop surfaces, one at least of which is a surface of revolution about the axis of the switch-actuating shaft, being provided on the shaft and rocking lever respectively, each pair being arranged to become engaged when the associated abutment surface moves out of engagement with its co-operating abutment and to act as a limit stop for the movement of the rocker lever without limiting the rotation of the switch actuating shaft. A self-centering spring is also provided, preferably a helical spring wound round the actuating shaft, the two ends of which project approximately radially side-by-side, and two dogs, one fixed to a frame and/ or housing and the other fixed to the actuating shaft, which project between the two projecting ends so as to tension the spring when the shaft is turned in either direction from a normal position.

In the drawing accompanying the specification FIG- URE 1 is a somewhat diagrammatic elevation of an embodiment of the invention seen at right angles to the axes of the rocker pivot and of the switch-actuating shaft, and

FIGURE 2 of the accompanying drawing similarly illustrates a modified embodiment.

Referring now first to FIGURE 1, a switching element 1 is fixed on a rotatable shaft 2 which may carry or operate switch contacts or the like in any convenient or conventional manner. The switching element co-operates with an actuating roller 3, which itself is mounted in a bearing block 3a movable in a radial slot 4 of a rocker lever 5 mounted on a pivot 6. A thrust spring 18 is arranged in the lever 5 to urge the block 3a and roller 3 away from the pivot 6 and against a plane surface 1a, of the switching element 1. The pressure of the spring 18 transmitted by the roller 3 upon the surface 1a produces a couple tending to turn the element 1 about the axis of the shaft 2, and this couple reverses its direction when the line of contact between the roller 3 and the surface 1a passes through the plane containing the axes of shaft 2 and roller 3. In order to ensure a sufficient build-up of stored energy in the spring 18 to ensure that the resultant switching operation takes place rapidly, two locking pawls 7 and 8, loaded by springs 26, are provided which prevent reversal of the position of element 1 by the pressure of roller 3 until the pawl in question has been moved out of engagement with the member 1 by abutment of the rocker lever 5 against end portions 7a and 8a of the pawls 7, 8, well after the passage of the roller 3 through the point at which the couple acting on element 1 changes its direction. In order to couple the movements of the rocker lever 5 to an actuator arm 9 which constitutes the primary actuating member and which may, for example, carry a roller 10 co-operating with suitable stop surface on a machine-tool slide, the arm 9 is fixed for common rotation on a switch-actuating shaft 11 provided with a cam member 12 in the form of two part-circular portions 13 and 14 of different diameters, both coaxial with the shaft 11 and adapted to cooperate respectively with opposite sides of a recess 15 in a forked end portion 16 of the actuating lever 5, opposite to the roller 3. The Width of the recess 15 is substantially equal to the sum of the radii of the part-circular portions 13 and 14 so that the cam member 12 will co-operate with the end portion 16 of rocker lever 5 to allow free movement of the actuator arm 9 within a limited range without moving the leverS, while the lever is held locked in one or the other of two end positions, except for a narrow range of positions of the switch-actuating shaft 11. The transition from each end of the part-circular portion 13 of the cam member 12 to the adjacent end of the part-circular portion 14 of smaller diameter is constituted by one of two cam surfaces 17 which are more or less radial to the axis of the actuating shaft 11 but slope outwardly at an angle, exceeding the friction angle, relative to a plane perpendicular to the radius from the axis of the pivot 6, and the end surfaces of the forked portion 16 of the lever 5 form abutments co-operating with these cam surfaces. Rotation of actuating arm 9 to the left from the position illustrated in the drawing toward its chain-dotted position will exert on rocker lever 5 a couple acting in a clockwise direction about the axis of pivot 6 so as to reverse lever 5 from its illustrated position to move its roller 3 beyond the neutral plane. After further movement lever 5 will then strike pawl 8, causing it to release the switching element 1, thus allowing the spring 18 to reverse the switching element 1. When the rocker lever 5 has reached this position, the inner side of the left-hand branch of the forked end 16 of the lever 5 will clear the larger-diameter cam portion 13 and thus allow further rotation of the cam member 12 and shaft 11 and thus of the actuator arm 9 without further movement of the rocker lever 5. On the contrary such further movement of rocker lever 5 will be prevented by abutment of the inner side of the right-hand branch of its forked end member 16 of lever 5 against the cam surface 14 of smaller radius.

In order to ensure that, when no force acts on the lever 9, the switch will assume one predetermined end position, the two upturned ends 19, 20 of a helical spring 21 encircling the shaft 11 straddle a dog 22 on the cam 12 and a stop 23 of equal width, secured in stationary switch housing 24, so that rotation of the cam 12 in either direction from a normal position will tension the helical spring 21. In order to permit the same parts to be used for making a switch which will stay in the righthand position or a switch which will stay in the left-hand position, the stop 23 is arranged asymmetrically in a symmetric dove-tail groove 24, a filler member 25 being provided to space the stop 23 from one side of the groove 24- and hold it in contact with the opposite side. By reversing the stop and filler member the position at which the switch will normally rest can be changed, While by using two filler members, one at each side, and each of half the width of the block 25, the lever 9 and cam member 12 can be biased to a central position.

Various features of the embodiment described with reference to the drawing may be modified within the scope of the invention. Thus the helical spring 21 may be replaced by a centering spring of different type, and a different type of trigger mechanism may be employed in- 9 stead of the illustrated combination of switching element 1 and pawls 7, 8.

FIGURE 2 of the accompanying drawing illustrates a modified embodiment, in which unchanged parts bear the same references as in FIGURE 1. This embodiment has been modified to enable the switch to be used as a stayput switch which will stay in either the right-hand position or the left-hand position or in a central position, whatever position it has been set to. With this object in view the stop 23 and filler member 25 have been replaced by a stop 28 the two end surfaces of which correspond respectively to that end surface of stop 23 which is in contact with one of the sides of the groove when the stop is in the position for producing a right-hand switch and a left-hand switch respectively, while the width of the dog 22 has been left unaltered. As a result the lever 9 can be moved throughout a range corresponding to the whole of the movement of the rocker lever, which in this embodiment bears the reference 5a, without making the dog 22 engage the spring arms 19 or 20, so that the spring 21 is only employed to intercept such excess movement of the lever 9 as is permitted by the circular cam surfaces 13 and 14. The pawls 7 and 8 have been replaced by modified pawls 29 which have stepped recesses 30, 31 for engagement with the dogs 32 of the switching element 1, the deeper recess 30 serving to retain the switching element 1 in one of its end positions until, on reaching its centre position, the rocker lever 5a has moved the pawl 29 sufficiently for the dog 32 to clear the deeper recess 30 and to engage the shallower recess 31, which allows the element 1 to move to its centre position, by which time the opposite pawl has, due to the movement of the lever 5a, been allowed to move under the action of its spring 26, to a position in which its recess 31 engages. the other dog 32 of the switching member, which is thereby locked in its centre position. When, upon further movement of the arm 9, the rocker lever 5a has moved to nearly its opposite end position, the pawl 29 is moved by the lever 5a to cause the first-mentioned dog 32 to clear also the second recess 31, thus allowing the switching element 1 to complete its switching operation and become locked in the other end position by engagement of its other dog 32 with the recess 31 of the second pawl 29.

In order to facilitate arresting of the switch in the neutral position, the bearing blocks 3a and roller 3 may be replaced as shown by an actuator block 33 having a fiat end surface 39. If, instead of allowing the switchactuating arm 9 free movement within the switching range, it is desired for the arm to normally assume a central position, this can be readily achieved by using a symmetrically arranged strip block 28 the active part of which has the same width as the dog 22, or alternatively by using the stop 23 of FIGURE 1 at the centre of the groove 24, located by two filler pieces, each half the width of filler piece 25, and arranged respectively at the two ends of the groove. The switch as shown in FIGURE 2 is so constructed that by simple reversal of the pawls 29 together with replacement of block 28 by stop 23 and a filler piece of FIGURE 1 and simultaneous replacement of the actuator block 33 by a bearing block and roller as shown at 3a and 3 in FIGURE 1 it can be modilied to operate exactly as the switch illustrated in FIG- URE 1. In order to achieve this, each pawl 29 has two pivot holes 34 and 35, one at each end, and is provided, in addition to the grooves 30 and 31 which are operative when the pivot hole 34 is in use, with a further recess 36 the operative edge of which has the same spacing from pivot hole as the edge of recess 30 has from pivot hole 34, and the socket 37 adjacent to pivot hole 34 for cooperation with spring 26 is duplicated by a similar spring socket 38 adjacent to pivot hole 35.

What we claim is:

l. A movement-control switch device for the termination or reversal of the movement of a motor-driven element, comprising a switch frame structure, a switching element movable relative to said structure between two switching positions, a rocker lever pivoted in said structure for movement about a fulcrum axis between two terminal positions to reverse the position of the switching element when the rocker lever is moved from either of its terminal positions to the other, over-centre resilient coupling means interposed between the rocker lever and the switching element, a switch-actuating shaft rotatable about its axis in said structure and having a pair of abutment members rotatable with it, the rocker lever having a pair of abutment surfaces for respective co-operation with said abutment members, said abutment surfaces being arranged on the rocker lever symmetrically at opposite sides of a plane which when the rocker lever is halfway between the said terminal positions, contains said fulcrum axis and the axis of the switch-actuating shaft, said surfaces being inclined inwardly to form an acute angle with a radial plane containing said fulcrum axis, the mutually adjacent edges of said abutment surfaces being so positioned that each said surface will move out of engagement with the associated abutment member when the rocker lever reaches one of its terminal positions, two cooperating pairs of stop surfaces, the surfaces of one at least of said pairs being surfaces of revolution about the axis of the switch-actuating shaft, the stop surfaces of each pair being respectively associated with said abutment members, and said stop surfaces being so positioned on the shaft and rocking lever respectively as to become engaged to lock the rocking lever in position without limiting the rotation of the switch-actuating shaft when either abutment surface moves out of engagement with the asso ciated abutment member, a centering spring having two ends extending approximately radially of the switch-actuating shaft in spaced side-by-side relation to each other, a stationary dog fixed in said frame structure, and a second dog fixed to the actuating shaft, both said dogs projecting between said radial ends of the centering spring in axially spaced relation so as to tension the spring when the switch-actuating shaft is turned from a central position by more than half the difference of the angles about the axis of the shaft respectively sub-tended by the two dogs.

2. A switch device as claimed in claim 1, wherein the two dogs sub-tend equal angles.

3. A switch device as claimed in claim 1, wherein the difference of the angles sub-tended corresponds to the angle of rotation of the shaft required for reversal of the switching element.

4. A switch device as claimed in claim 1, wherein the centering spring is a helical spring wound round the actuating shaft.

5. A switch device as claimed in claim 1, wherein the stationary dog is rem-ovably mounted in a seating provided in the frame structure.

6. A switch as claimed in claim 5, wherein the stationary dog is arranged asymmetrically relative to its seating so as to locate the shaft in a position corresponding respectively to one or the other end position of the switching member when the dog is mounted in a seating in two mutually reversed positions.

7. A switch device as claimed in claim 1, wherein the two dogs sub-tend different angles, further comprising a switch-locking member mounted for joint pivotal movement with the switching element and having two abutment portions, two pawls of each mounted in the frame structure for pivotal movement towards and away from the joint fulcrum axis of the switching element and locking member to respectively lock the latter unilaterally against movement from one or the other of its two switching positions, and pivotal movement away from said axis to release such locking engagement, and spring means urging the pawls into such locking engagement, said pawls having each two locking faces, one operative when the switching element is on one of its switching positions, and the other operative when the switching element is an intermediate neutral position, and said pawls being so arranged as to be respectively engaged and moved by the rocking lever to release the locking member from said first face when the rocking lever has passed its dead-centre position, and to release the locking member from said second locking face when the rocking lever approaches the end of its stroke for reversal of the position secured by the respective pawl.

8. A switching device as claimed in claim 7, wherein each pawl is reversibly mounted on its pivot and provided with a third abutment face which, when the pawl is reversed, is operative instead of said first and second faces,

the pawl being so shaped that when thus reversed it is actuated by the rocking lever to release the locking member for full movement of the switching element from one to the other of the switching positions when the rocking lever approaches its position corresponding to said other switching position, the device further including means for equalising the angles sub-tended by the two dogs.

No references cited.

BERNARD A. GILHEANY, Primary Examiner. ROBERT K. SCHAEFER, Examiner. 

1. A MOVEMENT-CONTROL SWITCH DEVICE FOR THE TERMINATION OR REVERSAL OF THE MOVEMENT OF A MOTOR-DRIVEN ELEMENT, COMPRISING A SWITCH FRAME STRUCTURE, A SWITCHING ELEMENT MOVABLE RELATIVE TO SAID STRUCTURE BETWEEN TWO SWITCHING POSITIONS, A ROCKER LEVER PIVOTED IN SAID STRUCTURE FOR MOVEMENT ABOUT A FULCRUM AXIS BETWEEN TWO TERMINAL POSITIONS TO REVERSE THE POSITION OF THE SWITCHING ELEMENT WHEN THE ROCKER LEVER IS MOVED FROM EITHER OF ITS TERMINAL POSITIONS TO THE OTHER, OVER-CENTRE RESILIENT COUPLING MEANS INTERPOSED BETWEEN THE ROCKER LEVER AND THE SWITCHING ELEMENT, A SWITCH-ACTUATING SHAFT ROTATABLE ABOUT ITS AXIS IN SAID STRUCTURE AND HAVING A PAIR OF ABUTMENT MEMBERS ROTATABLE WITH IT, THE ROCKER LEVER HAVING A PAIR OF ABUTMENT SURFACES FOR RESPECTIVE CO-OPERATION WITH SAID ABUTMENT MEMBERS, SAID ABUTMENT SURFACES BEING ARRANGED ON THE ROCKER LEVER SYMMETRICALLY AT OPPOSITE SIDES OF A PLANE WHICH WHEN THE ROCKER LEVER IS HALFWAY BETWEEN THE SAID TERMINAL POSITIONS, CONTAINS SAID FULCRUM AXIS AND THE AXIS OF THE SWITCH-ACTUATING SHAFT, SAID SURFACES BEING INCLINED INWARDLY TO FORM AN ACUTE ANGLE WITH A RADIAL PLANE CONTAINING SAID FULCRUM AXIS, THE MUTUALLY ADJACENT EDGES OF SAID ABUTMENT SURFACES BEING SO POSITIONED THAT EACH SAID SURFACES WILL MOVE OUT OF ENGAGEMENT WITH THE ASSOCIATED ABUTMENT MEMBER WHEN THE ROCKER LEVER REACHES ONE OF ITS TERMINAL POSITIONS, TWO COOPERATING PAIRS OF STOP SURFACES, THE SURFACES OF ONE AT LEAST OF SAID PAIRS BEING SURFACES OF REVOLUTION ABOUT THE AXIS OF THE SWITCH-ACTUATING SHAFT, THE STOP SURFACES OF EACH PAIR BEING RESPECTIVELY ASSOCIATED WITH SAID ABUTMENT MEMBERS, AND SAID STOP SURFACES BEING SO POSITIONED ON THE SHAFT AND ROCKING LEVER RESPECTIVELY AS TO BECOME ENGAGED TO LOCK THE ROCKING LEVER IN POSITION WITHOUT LIMITING THE ROTATION OF THE SWITCH-ACTUATING SHAFT WHEN EITHER ABUTMENT SURFACE MOVES OUT OF ENGAGEMENT WITH THE ASSOCIATED ABUTMENT MEMBER, A CENTERING SPRING HAVING TWO ENDS EXTENDING APPROXIMATELY RADIALLY OF THE SWITCH-ACTUATING SHAFT IN SPACED SIDE-BY-SIDE RELATION TO EACH OTHER, A STATIONARY DOG FIXED IN SAID FRAME STRUCTURE, AND A SECOND DOG FIXED TO THE ACTUATING SHAFT, BOTH SAID DOGS PROJECTING BETWEEN SAID RADIAL ENDS OF THE CENTERING SPRING IN AXIALLY SPACED RELATION SO AS TO TENSION THE SPRING WHEN THE SWITCH-ACTUATING SHAFT IS TURNED FROM A CENTRAL POSITION BY MORE THAN HALF THE DIFFERENCE OF THE ANGLES ABOUT THE AXIS OF THE SHAFT RESPECTIVELY SUB-TENDED BY THE TWO DOGS. 